Is there something odd about my Omega 105.012 ?

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To me it looks like a B2 MK2 dial as mentioned above. I believe these two very detailed articles linked below will answer your concerns about the case and dial.

https://www.chronoholic.com/blog

Without the Omega Extract I don’t think anyone can say for sure about the serial number either way. Other than it is outside of the commonly accepted range.
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Thanks for some updated photos. These do provide enough clarity to give some judgments on.
I would say the dial is a B2 MK2 dial. This lines up with the movement serial number.

The case is still unclear from the photos.

If you have access to a pair of calipers you can measure this part of the case to help define it.